Crashing on teardown.

Bug: angleproject:5989
Change-Id: Ie5560f4e1dee310f5f08a7bca83a0506c20f6920
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2904126Reviewed-by: Cody Northrop <cnorthrop@google.com>
Commit-Queue: Cody Northrop <cnorthrop@google.com>